I wear a camelback rocket. It rides fairly high on my back, but I'm a 6'2" dude. The road tours I'm on around here about half the riders (guys and gals)wear camelbacks of some sort. The newer camelbacks have wide padded straps so the don't cut into your shoulder.I was once riding down a valley (about40 mph) and being overtaken by a rider with the seat mounted rear bottle carrier.It was shortly after the start and his big bottles were full and the road was rough.One contraction joint too many and the carrier broke off and sent the bottles flying.That was a bad way to start a century.